TimersTimers

Mechanical Timing RelayMechanical Timing Relay

Time delay relays are simply control relays Time delay relays are simply control relays with a time delay built in.with a time delay built in.

Their purpose is to control an event based Their purpose is to control an event based on time.on time.

TimersTimers

• On delay : On delay : With an on-delay timer, timing begins when With an on-delay timer, timing begins when coil is activated. When the time has expired, the contacts coil is activated. When the time has expired, the contacts close/open(depends on the contacts normal condition) — and close/open(depends on the contacts normal condition) — and remain closed/opened until coil is de-activated. If coil is de-remain closed/opened until coil is de-activated. If coil is de-activated before time-out, the time delay resetsactivated before time-out, the time delay resets

• Off delay :Off delay :When using an off-delay timer, when coil is When using an off-delay timer, when coil is activated, the contacts close/open (depends on the contacts activated, the contacts close/open (depends on the contacts normal condition). De-activating the coil causes timing to begin. normal condition). De-activating the coil causes timing to begin. When the time has expired, the contact will return to their normal When the time has expired, the contact will return to their normal state. state.

Normally-open, timed-closed ContactNormally-open, timed-closed Contact

NOTC (normally open, timed close contact)- contact is open, when relay is de energized; when relay is energized, there is a time delay in closing.

Normally-open, timed-closed Normally-open, timed-closed ExampleExample

normally closed, timed open contactnormally closed, timed open contact

NCTO (normally closed, timed open contact)-contact is closed when relay coil is de energized. When relay is energized, there is a time delay in opening.

normally closed, timed open examplenormally closed, timed open example

Normally open, timed open contact

NOTO (Normally open, timed open contacts)- contact is normally open, when relay coil is de energized when relay coil is energized contact closes instantly. When relay coil is de energized, there is a time delay before the contact opens.

Normally open, timed open contact example

normally closed, timed close contact

NCTC (normally closed, timed close contact)- contact is normally closed when relay coil is de energized. When the relay coil is energized, contact open instantly. When the relay coil is de energized, there is a time delay before the contact closes.

normally closed, timed close contact example

Timer instructionsTimer instructions

PLC timers are output instruction that provides PLC timers are output instruction that provides the same function as mechanical timing relay.the same function as mechanical timing relay.

•ON delayON delay provides the delay when the relay provides the delay when the relay is energized.is energized.

•OFF delayOFF delay provides the delay when the provides the delay when the relay is de energized.relay is de energized.

•Retentive Timer Retentive Timer is similar to on delay timer is similar to on delay timer except for the fact that the Accumulated value except for the fact that the Accumulated value is retained even if the relay is de energized. is retained even if the relay is de energized.

On delay timer exampleOn delay timer example

On delay timer exampleOn delay timer example

off delay timer exampleoff delay timer example

On delay timer exampleOn delay timer example

Timer instructionsTimer instructions

SLC 500SLC 500 CompacLogixCompacLogix

Timer instructionTimer instruction

• Address: By default, SLC 500 uses file #4 for timers. Compactlogix Address: By default, SLC 500 uses file #4 for timers. Compactlogix uses tags.uses tags.

• Time Base: Time Base: SLC 500 uses SLC 500 uses 1.0s, 0.01s, 0.001s. CompactLogix uses 1.0s, 0.01s, 0.001s. CompactLogix uses only .001sonly .001s

• Preset value (pre): is the value up to which the timer will time.Preset value (pre): is the value up to which the timer will time.

• Accumulated value (ACC): is the value that increments as the Accumulated value (ACC): is the value that increments as the timer is timing. This value can range from 0 to +32,767.timer is timing. This value can range from 0 to +32,767.

• Done (DN) bit: Changes state whenever .PRE=.ACC valueDone (DN) bit: Changes state whenever .PRE=.ACC value

• Enable (EN) bit: is on when the timer instruction is true.Enable (EN) bit: is on when the timer instruction is true.

• Timer timing(TT) bit: is on when the timer is timing.Timer timing(TT) bit: is on when the timer is timing.

Timer memory structureTimer memory structure

SLC 500 timer memory structureSLC 500 timer memory structure

CompactLogix timer memory structureCompactLogix timer memory structure

On delay timer instruction On delay timer instruction

• When the TON is true, it will write a "1" to the EN (Enable).When the TON is true, it will write a "1" to the EN (Enable).

• If the TON is true and the ACC (Accumulated) is less than the PRE If the TON is true and the ACC (Accumulated) is less than the PRE (Preset), the TON will write a "1" to the TT (Timer Timing) bit and a (Preset), the TON will write a "1" to the TT (Timer Timing) bit and a "0" to the DN (Done) bit. "0" to the DN (Done) bit.

• If the TON is true and the ACC (Accumulated) is greater than the If the TON is true and the ACC (Accumulated) is greater than the PRE (Preset), the TON will write a "0" to the TT (Timer Timing) bit PRE (Preset), the TON will write a "0" to the TT (Timer Timing) bit and a "1" to the DN (Done) bit.and a "1" to the DN (Done) bit.

• The processor resets the accumulated value when the TON is The processor resets the accumulated value when the TON is false.false.

• Reset instruction (RES), will reset the timer at any time.Reset instruction (RES), will reset the timer at any time.

Off-Delay TimerOff-Delay Timer

• When a TOF is true, it will write a "0" to the When a TOF is true, it will write a "0" to the accumulated value, a "1" to the EN (Enable), accumulated value, a "1" to the EN (Enable), a "0" to the TT (Timer Timing), and a "1" to a "0" to the TT (Timer Timing), and a "1" to the DN (Done) bit.the DN (Done) bit.

• When the TOF is false, it will write a "0" to When the TOF is false, it will write a "0" to the EN (Enable).the EN (Enable).

• If the TOF is false and the ACC If the TOF is false and the ACC (Accumulated) is less than the PRE (Preset), (Accumulated) is less than the PRE (Preset), the TON will write a "1" to the TT (Timer the TON will write a "1" to the TT (Timer Timing) bit and a "1" to the DN (Done) bit.Timing) bit and a "1" to the DN (Done) bit.

• If the TOF is false and the ACC If the TOF is false and the ACC (Accumulated) is greater than the PRE (Accumulated) is greater than the PRE (Preset), the TOF will write a "0" to the TT (Preset), the TOF will write a "0" to the TT (Timer Timing) bit and a "0" to the DN (Done) (Timer Timing) bit and a "0" to the DN (Done) bit.bit.

• A reset instruction resets the timer A reset instruction resets the timer

Off delay timer operationOff delay timer operation

Retentive timerRetentive timer

The RTO instruction begins timing when it rung The RTO instruction begins timing when it rung goes true. As long as the rung remains true, the goes true. As long as the rung remains true, the timer updates the accumulated value each program timer updates the accumulated value each program scan, until it reaches the preset value. The RTO scan, until it reaches the preset value. The RTO instruction retains its accumulated value even if instruction retains its accumulated value even if one of the following occurs:one of the following occurs:•the rung goes false the rung goes false •you change to Program mode you change to Program mode •the processor faults of loses power the processor faults of loses power

SLC 500 Timer addressing SLC 500 Timer addressing ExampleExample

T4T4:0 means that it references an internal Timer file:0 means that it references an internal Timer fileT4:T4:00 means that it uses the first Timer in the table means that it uses the first Timer in the table

T4T4:0/:0/DNDN means that it references the Done bit. means that it references the Done bit.

T4T4:0/:0/ENEN means that it references the Enable bit. means that it references the Enable bit.

T4T4:0/:0/TTTT means that it references the Timer Timing bit. means that it references the Timer Timing bit.

T4:0.T4:0.ACCACC means that it references the 16 bit Accumulated value. means that it references the 16 bit Accumulated value.

T4T4:0.:0.PREPRE means that it references the 16 bit Reset value. means that it references the 16 bit Reset value.